Generally, waste heat generated in industrial facilities has mostly been discarded. There has been a growing interest in techniques to recover energy from waste heat in order to deal with fossil fuel depletion and reduce emission of greenhouse gases and emission of pollutants. Industrial waste heat has been continuously increasing, and commercialization of waste heat recovery techniques is important to achieve national greenhouse gas reduction targets.
Because a temperature of waste heat generated in industrial facilities is lower than a steam temperature of a thermoelectric power plant, it is difficult to apply an existing Rankine cycle utilizing steam of industrial facilities. Accordingly, an organic Rankine cycle (ORC) system utilizing an organic refrigerant which evaporates at a low temperature may be applied.
The ORC is a thermodynamic cycle which converts thermal energy into electrical energy. In order to obtain high energy conversion efficiency from a heat source in a low-temperature range, ORC uses a working fluid which evaporates at a low temperature. Freon, hydrocarbon-based organic medium, or the like is applied as the working fluid.
In order to increase a waste heat energy recovery amount in the Rankine cycle, a temperature difference and a pressure difference between an inlet and an outlet of a turbine should be large. Because conditions of a condenser, which is a low-temperature part, are not significantly different, the ORC efficiency increases as a temperature and a pressure of an organic refrigerant at the inlet of the turbine become higher. However, it is essential to design and operate the system so that the organic refrigerant does not exceed the critical conditions of temperature and pressure.
In the case of the ORC, when deviation from design conditions occurs, a condition of a working fluid at the inlet of the turbine may sharply change, and thus the overall energy recovery amount may significantly be reduced. A frequency at which the ORC is operated in off-design conditions is higher as compared with other power generation facilities, and thus it is difficult to maximize the waste heat recovery rate.
The related art of the present invention has been disclosed in Korean Unexamined Patent Application Publication No. 2013-0028537 (Date of Publication: Mar. 19, 2013, Title of Invention: Power Generation System).